Preframe presentations present
Preframes (directed complete posets with finite meets that distribute over the directed joins) are the algebras for an infinitary essentially algebraic theory, and can be presented by generators and relations. This result is combined with a general argument concerning categories of commutative monoids to give a very short proof of the localic Tychonoff Theorem.
It is also shown how frames can be presented as preframes, a result analogous to Johnstone's construction of frames from sites, and an application is given.
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